How did evolution create a society where most individuals do not raise their own offspring, but dedicate their lives to caring for others? Researchers claim to have identified a starting point for this evolutionary path in honey bees
Zvi Atzmon, Galileo
Some perceive natural selection, the cogwheel that drives evolution in the living world, as an all-in-all war, a constant battle in which "only the strong survive". According to this view, it is difficult to understand how in the living world there are distinct examples of cooperation and even altruism (selfishness) - sacrificing yourself for the sake of others. One of the prominent examples of this is the shared life of social insects, such as ants, termites and honey bees.
The honey bee society in the hive includes one female that lays eggs - the queen, several males and female queens that are not sexually active, do not mate and do not lay eggs - these are the workers. These asexual females, who work, take care of the only fertile female, the queen, who is a master, take care of and feed the maggots - their younger sisters (and very few of their brothers) who have hatched and have not yet become adult bees, clean, warm and ventilate the hive, collect food, produce honey and fight enemies . The food of the bees mainly includes pollen grains of flowers - protein food, and flower nectar rich in energy-providing sugars.
The worker bees have ovaries, but they "give up" laying eggs and raising offspring - that is, passing their genes on to the next generation; From a reproductive point of view they are therefore a dead end. And this matter certainly raises a question: how do genes that dictate individuals that carry the same traits of not passing on genes to offspring survive during evolution? And here, from a theoretical consideration, we will prove that if you do not breed yourself, but you worry that other individuals, who carry genes identical to yours, will breed, then genes like yours will be passed on to future generations.
Conflicting interests
A clear example of this is our body cells: the majority of our body cells end their lives without the genes contained in them being passed on to the offspring. The only body cells (if it is not a clone) that may directly transfer their genes to offspring are the cells that form gametes. But if a heart cell helps, through its contractions, to supply blood to the reproductive organs, then it increases the chances of the reproductive cells to produce offspring. Thus the genes in the heart cell (and kidney, liver and brain cells) are passed on to the next generation through their identical copies found in the reproductive cells.
In social bees, the situation is more "tense" in terms of interests - the genes in the worker's body are not the same as the queen's genes: only half of the worker's genes originate from the mother, while the other half originate from the father, the male who mated with the queen when she was young. Genetically, the bee is three-fourths close to her sisters on average: the half that originates from the father is equal in all of them (which is not the case with human female sisters! - the reason is that the male bee is haploid, so that his spermatozoa contain the same set of genes as his body's cells; he has no reduction division) and another half of The mother's genes. Therefore, a worker who takes care of her sisters is actually taking care of the genes, on average 75% of which are identical to her genes.
In any case, it must be remembered that the genes of the worker are not the same as those of the queen, so it is impossible to see the queen as an "extracorporeal ovary" of the worker. In addition to that, the body of the worker has ovaries, although as usual they are not used by her. If this is the case, the question remains in all its poignancy: How did evolution create a bee society, which includes masses of workers who "give up" their fertility and who do not pass on their genes to their offspring? Gro Amdam from the University of Arizona and her colleagues believe that they have found the end of the thread, the evolutionary bridgehead for the development of the complex society of honey bees. In an article they published in "Nature", Amdam and her colleagues point to the life stages that characterize bees living in the vine (solitary, non-social bee species) as the basis from which the evolution of a complex and altruistic bee society began.
Freedom or shared life?
Non-social bees (solitary bees) collect pollen during the periods when they lay eggs and take care of the young caterpillars, while when they are free from these maternal duties, they feed mainly on nectar. And here, the researchers found that among the active honeybees, it is possible to identify those that collect pollen the most and those that collect nectar the most. The researchers compared these two groups of workers, and also examined two strains of bees that Robert Page (Page, one of the authors of the current article in Nature) had previously cultivated for the primary collection of pollen or for the multiple collection of nectar.
It turned out that both in the worker bees of normal honey bees, and in strains specially cultivated to prefer pollen or nectar, the pollen collections have a higher affinity for fertility than the nectar collections, so that the two types of workers represent different stages in the life of a solitary bee. This is manifested in the fact that the ovaries of the pollen collectors are more developed than the ovaries of the nectar collectors, and they also produce a larger amount of the protein vitellogenin, which is used as a raw material to create the egg yolk. And yet: when the pollen collections reach the age of leaving the hive to collect food, their "blood" (insect blood does not contain hemoglobin, is not red, and is called hemolymph) contains a relatively high level of the youth hormone, a hormone responsible for sexual maturation in insects, compared to the nectar collections.
As mentioned, workers do not lay eggs even though there are ovaries in their bodies - the presence of a queen suppresses (through pheromones) the production of eggs among the workers. And here, when the researchers transferred bees to colonies (hives) that were without a queen, about two weeks later it was found that a very high percentage of the pollen collectors had active ovaries, while the percentage of the nectar collecting workers whose ovaries became active was much lower.
Gro Amdam and her colleagues did not pretend, of course, to decipher all the details of the evolutionary path that led from solitary, non-social bees to the honey bee society, but according to them they identified the beginning of the path, the starting point for the evolution of an altruistic society. According to them, the reproductive behavior of the ancient bees, who did not live in societies like today's honey bees, and its connection to a preference for protein or sugary food, is the bridgehead for the formation of the complex honey bee society.
